This invention is in the field of sewing machines; more particularly, it is concerned with a device which prevents removal of a belt guard without some initial deliberate act designed to alert a person to the potential for bodily harm and deter removal by unauthorized persons.
Belt guards have been used with sewing machines for many years for the purpose of protecting a sewing machine operator and other persons from injury due to entrainment of clothing or physical entanglement with moving parts of the sewing machine. An early form of sewing machine belt guard is shown in the U.S. Pat. No. 947,651 issued on Jan. 25, 1910 to Schreiber and discloses a belt guard which covers the handwheel end of a sewing machine in such a fashion as to permit limited access to the handwheel for rotation thereof, but cover a belt and pulley portion thereof to protect an operator against the dangers recited above. The belt guard disclosed in the above patent is fastened to the sewing machine bed with a hook which could be removed to swing the belt guard away for access to the belt, but the belt guard is available for protection during operation of the sewing machine when the operator's attention was diverted elsewhere.
A more recent belt guard is disclosed in the U.S. Pat. No. 2,790,407, issued on Apr. 30, 1957 to Andres, which discloses a belt guard pivotably carried by a fixture attached to a sewing machine table, which belt guard was suitable for use with a variety of sewing machines which might be installed in that specific table. In a most recent prior art belt guard, predecessor to this invention, the belt guard itself is provided with a pivot rod extending between ears thereof, the pivot rod being slabbed on opposite sides thereof on the extremities adjacent the ears of the guard. A pivot frame was provided with lugs upstanding adjacent the ears of the belt guard, the lugs having slots therein extending to apertures which fit about the pivot rod. In operation the belt guard could be rotated until the slabbed portions of the pivot rod align with the slots in the pivot frame permitting access of the pivot rod to the apertures in the upstanding lugs. Thus, the belt guard could be removed rather readily for service by swinging back the belt guard until the slabbed surfaces were aligned with the slots in the pivot frame and removed therefrom. Unfortunately, the ease of removal of the belt guard contributed to frequent operation of the sewing machine without the belt guard due to removal thereof by the sewing machine operator.
What is required is some means for preventing ready removal of the belt guard from the sewing machine by a sewing machine operator, but retain this ease of removal feature for a maintenance or repair person.